What is this Cache.db file?

Thank you very much!
Actually, since I was in Combo Cleaner, I deleted them with this application.
I have another question for you, if you can answer it and if you know Combo Cleaner. At one point, this app indicated my duplicates, and I removed a few, but there were still almost 1000 left. I intended to stop the cleaning because it took too long to check each folder before deleting them. I don't know what happened, or what I did, but suddenly there were only 27 folders left. This bothers me a lot because I don't know where the others I didn't check went. Was it a mistake on my part? It’s possible. I would like to recover the deleted folders, but I haven't found how to do it or if it's possible.
Could you help me with that, please?
Thanks anyway!
Sylvie :)

Hello,

To delete cache files, you just need to use Onyx, which does a great job cleaning up these useless files.
You didn’t mention your Mac model or which OS X it’s running, and we’re not fortune tellers, so here’s how to use Onyx:

You need to download Onyx for your OS here:

https://www.titanium-software.fr/en/onyx.html

After installation,
Launch Onyx and follow Francis’s good advice.
-Let it check the SMART status of the hard drive and the structure of the volume (note: this operation cannot be performed if the hard drive is not journaled)
-then give it the password when it asks
-next click on the "Automation" button ?
-check all the boxes except "Show folder contents"
-click on "Execute"
-It will take a while, be patient.
-Restart the Mac

© Sanspseudo (Francis)

Note: the first startup after running Onyx is a bit slow, that’s normal, the following ones will be normal.

Under Sierra and above

https://forums.commentcamarche.net/forum/affich-35262220-onyx-pour-high-sierra

Happy cleaning and optimizing.

--
When it's urgent, it's already too late (Talleyrand)
When everything has failed, read the manual ;)